iPhoto is a JPEG processing application. It can import RAW, but it will immediately create a JPEG version of the image and THAT is the version of the image that will be adjusted. If you shoot RAW, you don't want to use iPhoto.
The most popular application for RAW workflow is Adobe Lightroom. In theory you can still "buy" Lightroom but I've noticed they really hide this ... Adobe wants you to "rent" Lightroom. They have a photography package that includes unlimited use of Lightroom and Photoshop for $10/month but they require a minimum 1 year subscription (they'll let you pay all $120 up front... but you can also just pay $10 per month each month, you don't have to pay up-front.)
The free option is to use Canon's Digital Photo Professional (DPP) which also knows how to deal with Canon RAW files. While DPP does a good job, the nice thing about Lightroom is that you do a full import to your photo library and you can easily move from image to image (rather than DPP where you have to open and process each image one-at-a-time and save each image one-at-a-time.) Lightroom is handling management of your photo libraries in addition to being the image adjustment application.
I've only recently converted to Lightroom. I previously used Apple Aperture, but Apple has announced that they will not be continuing development on Aperture, so I don't recommend you use that.